1. Field of the Invention
The present invention relates to liquid crystal display (LCD) devices, and more particularly, to an LCD device which is capable of preventing degradation of the device.
2. Background of the Related Art
Among various of flat displays, the LCD device is in great demand because of great contrast ratio, small power consumption, and suitability for displaying gradation and moving pictures. The LCD device is usually provided with an LCD Module (LCM) and a driving circuit unit for driving the LCD module. The LCD module has a liquid crystal panel unit with switching devices for switching signals provided to a matrix of liquid crystal cells injected between two sheets of glass, and a back light unit for directing light to the liquid crystal panel unit.
The liquid crystal panel unit and the back light unit are held together as one unit and protected with a case from an external impact. The driving circuit unit is mounted on a printed circuit board (PCB) to drive the liquid crystal panel unit. A tape carrier package (TCP) is used for signal transmission between the liquid crystal panel unit and the PCB. The TCP is structured such that single or multiple metallic conductive layers are inserted between soft material layers, for example, polyamide layers or the like.
A related art LCD device will be described with reference to the attached drawings. FIG. 1 schematically illustrates a disassembled perspective view of a related art LCD module. FIG. 2 schematically illustrates a back view of the related art LCD device of FIG. 1. FIG. 3 schematically illustrates a cross-sectional view taken along a line I-I′ in FIG. 2.
As shown in FIG. 1, an LCD module 10 is provided with a liquid crystal panel unit 11 and a back light unit 12, which are held together with a main support 13 and a top case 20. Although not shown, all of the above units are placed in and fastened to a bottom case. The main support 13 is a mold of plastic material for accommodating the back light unit 12 and the liquid crystal panel unit 11. The back light unit 12 includes a lamp 25, a reflective plate 12a, a light guide plate 12b and optical sheets 12c-12e. The liquid crystal panel unit 11 includes top and bottom substrates 11c and 11d bonded opposite to each other, and polarization plates 11a and 11b sandwiching the top and bottom substrates 11c and 11d. 
The optical sheets 12c-12e of the back light unit 12 represent a diffuser sheet 12c, a prism sheet 12d and a protection sheet 12e, respectively. The top substrate 11c of the liquid crystal panel unit 11 is provided with a color filter layer for displaying colors. The bottom substrate 11d of the liquid crystal panel unit 11 is provided with thin film transistors as switching devices for turning on/off a voltage. Therefore, light from the lamp 25 is lead through the light guide plate 12b, passes through the optical sheets 12c-12e in succession, and reaches to the liquid crystal panel unit 11 on which picture information is displayed.
The picture information is received from a driving circuit unit, which includes printed circuit boards 40a and 40b attached to the bottom substrate 11d of the liquid crystal panel unit 11. As shown in FIG. 2, the printed circuit boards 40a and 40b are mounted to a back of the main support 13. The printed circuit boards 40a and 40b each have a drive integrated circuit (IC) for driving the switching devices (the TFT array). Specifically, the printed circuit board 40a represents a data printed circuit board having a data drive IC mounted thereon, and the printed circuit board 40b represents a gate printed circuit board having a gate drive IC mounted thereon. As shown in FIGS. 2 and 3, the data printed circuit board 40a is also provided with a timing controller (not shown) for controlling a data drive signal, a power supplying unit 50 for supplying power for various signals, and a connector 60 for connection to an external power source. The printed circuit boards 40a and 40b are electrically connected to the liquid crystal panel unit 11 via tape carrier packages 41a and 41b, to transmit control signals and video signals from the drive ICs to the LCD module 10.
Next, an assembly process of the LCD device will be described with reference to FIGS. 1 and 3.
As shown in FIG. 3, the back light unit 12 is arranged inside the main support 13 by stacking the lamp 25, the reflective plate 12a, the light guide plate 12b, and the optical sheets 12c-12e in succession. The liquid crystal panel unit 11 has the polarization plates 11a and 11b to sandwich the top and bottom substrates 11c and 11d. Also, the liquid crystal panel unit 11 is seated on a step of the main support 13 to be spaced a distance from the back light unit 12. Then, the tape carrier packages 41a and 41b attached to the bottom substrate 11d of the liquid crystal panel unit 11 are folded to surround a lower edge of the main support 13. Thus, the printed circuit boards 40a and 40b are arranged on the back of the main support 13.
By supplying power to the LCD device through the connector 60 of FIG. 2, and turning on the lamp 25, the LCD device is driven but is liable to degrade due to heat from the power supply part 50 of FIG. 2. In order to prevent the LCD device from being degraded, as shown in FIG. 2, a conductive tape 70 is provided between a part of the printed circuit board 40a where the heat is generated and the liquid crystal module 10. Specifically, as shown in FIG. 3, the conductive tape 70 is arranged between the printed circuit board 40a and the main support 13. The conductive tape 70, a conductive aluminum film, is attached to the printed circuit board 40a. 
However, the related art LCD device has at least the following problem. When the printed circuit board is provided to the back of the LCD module, heat from the power supply unit and the like affects the liquid crystal layer and the polarization plates, thereby causing degradation of the LCD module.
In order to resolve the problem of degradation of the device, a conductive tape is inserted between the part of the printed circuit board having the heat emitted therefrom and the LCD module, to disperse the heat. However, since the conductive tape is attached manually, there are many defects of the attachment depending on working states of the attachment of the workers. Further, since such a conductive tape may transfer the heat directly to the LCD module, the heat cannot be efficiently dispersed to the outside of the LCD device.